1. Liquids Forces Between Liquid Molecules and their Effect on the Properties of Liquids

2. Types of Forces Intramolecular-forces within a molecule- bonding types Intramolecular-forces within a molecule- bonding types examples: ionic and covalent Intermolecular-forces between molecules Intermolecular-forces between molecules examples: ionic, dispersion, dipole-dipole, and hydrogen bonding and hydrogen bonding

3. Ionic Forces Exist between “molecules” that contain ionic bonds. Exist between “molecules” that contain ionic bonds. Result from the electrostatic charges within the Result from the electrostatic charges within thecompound. Opposite charges attract. Opposite charges attract. Strongest type of intermolecular force. Strongest type of intermolecular force.

4. London Dispersion Forces Exist between noble gas atoms and nonpolar molecules Exist between noble gas atoms and nonpolar molecules Weakest Weakest Temporary-as electrons move around the nucleus, a momentary asymmetrical distribution of electrons can occur (provides a temporary dipole) Temporary-as electrons move around the nucleus, a momentary asymmetrical distribution of electrons can occur (provides a temporary dipole) The instantaneous dipole can induce a similar dipole in a neighboring atom The instantaneous dipole can induce a similar dipole in a neighboring atom

5. London Dispersion Forces (continued) Large atoms with many electrons have stronger London Dispersion Forces Large atoms with many electrons have stronger London Dispersion Forces Larger nonpolar molecules have stronger LD forces Larger nonpolar molecules have stronger LD forces

6. Which has the stronger LD force? 1. Cl 2 2. Br 2

7. Which has the stronger LD force? 1. CH 4 2. C 2 H 6 3. C 4 H 10

8. Which has the stronger LD force 1. He 2. Ne 3. Ar 4. Xe

9. Dipole-Dipole Forces Exist between polar molecules Exist between polar molecules Permanent Permanent Stronger than London Dispersion Forces Stronger than London Dispersion Forces (1% as strong as ionic/covalent bonds) (1% as strong as ionic/covalent bonds) Created through an unequal sharing of electrons which results in a partial negative and positive charge Created through an unequal sharing of electrons which results in a partial negative and positive charge Positive end of one molecule attracts the negative end of another molecule Positive end of one molecule attracts the negative end of another molecule

10. Which of the following molecules have dipole-dipole forces present? 1. NH 3 2. CH 4 3. Both

11. Which of the following molecules have dipole-dipole forces? 1. CO 2 2. H 2 0 3. Both

12. Which of the following molecules have dipole-dipole forces present? 1. SF 4 2. SF 6 3. Both

13. Hydrogen Bonding A specific type of dipole-dipole force A specific type of dipole-dipole force Occurs when hydrogen atoms are bonded to highly electronegative atoms such as N, O, or F. Occurs when hydrogen atoms are bonded to highly electronegative atoms such as N, O, or F. Created because of high levels of polarity and small size of hydrogen atoms (especially strong dipole-dipole attraction occurs) Created because of high levels of polarity and small size of hydrogen atoms (especially strong dipole-dipole attraction occurs)

14. Which of the following compounds has hydrogen bonding present? 1. CH 4 2. CH 3 OH 3. Both

15. Which of the following compounds has hydrogen bonding present? 1. H 2 S 2. H 2 O 3. Both

16. Which of the following compounds has hydrogen bonding present? 1. HCl 2. HF 3. Both

17. Review of Intermolecular Forces Identify the most important type of interparticle forces present in each of the following substances. Identify the most important type of interparticle forces present in each of the following substances. Ar Ar HCl HCl HF HF CaCl 2 CaCl 2 CH 4 CH 4 CO CO NaNO 3 NaNO 3

18. What is the most importance type of interparticle force present in Ar? 10 1. Ionic 2. London Dispersion 3. Dipole-Dipole 4. Hydrogen Bonding 1234567891011121314151617181920 21222324252627282930

19. What is the most important type of interparticle force present in HCl? 10 1. Ionic 2. London Dispersion 3. Dipole-Dipole 4. Hydrogen Bonding 1234567891011121314151617181920 21222324252627282930

20. What is the most important type of interparticle force present in HF? 10 1. Ionic 2. London Dispersion 3. Dipole-Dipole 4. Hydrogen Bonding 1234567891011121314151617181920 21222324252627282930

21. What is the most important type of interparticle force present in CaCl 2 ? 10 1. Ionic 2. London Dispersion 3. Dipole-Dipole 4. Hydrogen Bonding 1234567891011121314151617181920 21222324252627282930

22. What is the most important type of interparticle force present in CH 4 ? 10 1. Ionic 2. London Dispersion 3. Dipole-Dipole 4. Hydrogen Bonding 1234567891011121314151617181920 21222324252627282930

23. What is the most important type of interparticle force present in CO? 10 1. Ionic 2. London Dispersion 3. Dipole-Dipole 4. Hydrogen Bonding 1234567891011121314151617181920 21222324252627282930

24. What is the most important type of interparticle force present in NaNO 3 ? 10 1. Ionic 2. London Dispersion 3. Dipole-Dipole 4. Hydrogen Bonding 1234567891011121314151617181920 21222324252627282930

25. Arrange the following molecules in order of decreasing intermolecular interaction: SO 2, Cl 2, CH 3 OH, CH 3 NH 2 10 1. CH 3 OH > CH 3 NH 2 >SO 2 >Cl 2 2. Cl 2 >SO 2 >CH 3 OH>CH 3 NH 2 3. SO 2 >CH 3 NH 2 >CH 3 OH>Cl 2 4. CH 3 NH 2 >CH 3 OH>SO 2 >Cl 2 1234567891011121314151617181920 21222324252627282930

26. Properties of Liquids

27. Surface Tension Resistance of a liquid to increase in surface area Resistance of a liquid to increase in surface area Measure of the inward forces Measure of the inward forces Liquids with high intermolecular forces have high surface tensions Liquids with high intermolecular forces have high surface tensions

28. Capillary Action Spontaneous rising of a liquid in a narrow tube Spontaneous rising of a liquid in a narrow tube Caused by cohesive and adhesive forces Caused by cohesive and adhesive forces cohesive forces-intermolecular forces among liquid molecules among liquid molecules adhesive forces- force between the liquid adhesive forces- force between the liquid molecules and the container; occur when molecules and the container; occur when the container is made of a polar substance the container is made of a polar substance

29. Example of Capillary Action When water is placed in a glass graduated cylinder, the meniscus is concave When water is placed in a glass graduated cylinder, the meniscus is concave adhesive forces > cohesive forces (glass is polar) When mercury is placed in the same graduated cylinder, the meniscus is convex When mercury is placed in the same graduated cylinder, the meniscus is convex cohesive forces > adhesive forces (mercury contains only dispersion forces-nonpolar)

30. Viscosity A resistance to flow A resistance to flow Strong intermolecular forces result in high viscosity Strong intermolecular forces result in high viscosity Large molecules also have high viscosity due to greater LD forces Large molecules also have high viscosity due to greater LD forces As temperature increases, viscosity decreases As temperature increases, viscosity decreases

31. Vapor Pressure Pressure of vapor above the surface of a liquid Pressure of vapor above the surface of a liquid Caused when the molecules on the surface break away and go into the gas phase Caused when the molecules on the surface break away and go into the gas phase In order to break away, the molecules must possess a minimum amount of kinetic energy In order to break away, the molecules must possess a minimum amount of kinetic energy High intermolecular forces result in low vapor pressures High intermolecular forces result in low vapor pressures Volatile liquids are liquids that evaporate rapidly resulting in high vapor pressures Volatile liquids are liquids that evaporate rapidly resulting in high vapor pressures

32. Vapor Pressure (continued) Substances with weak intermolecular forces tend to be volatile Substances with weak intermolecular forces tend to be volatile As temperature increases, vapor pressure increases (more molecules possess the minimum kinetic energy and the rate of evaporation increases) As temperature increases, vapor pressure increases (more molecules possess the minimum kinetic energy and the rate of evaporation increases) See the diagram on page 487. See the diagram on page 487.

33. Calculating Vapor Pressure The equation used to calculate the vapor pressure is: The equation used to calculate the vapor pressure is: ln (P vapT1 ) = ∆Hvap(1 - 1) (P vapT2 ) = R (T 2 - T 1 ) (P vapT2 ) = R (T 2 - T 1 ) ∆H is the heat of vaporization in J/mol, T is Kelvin temperature, R is 8.314 J/Kmol, and P vap is vapor pressure

34. Practice Problem In Breckenridge, Colorado, the typical atmospheric pressure is 520. torr. What is the boiling point of water (∆H vap = 40.7 kJ/mol) in Breckenridge? In Breckenridge, Colorado, the typical atmospheric pressure is 520. torr. What is the boiling point of water (∆H vap = 40.7 kJ/mol) in Breckenridge?

35. Melting Point and Boiling Points Melting point- temperature at which the solid and liquid have the same vapor pressure Melting point- temperature at which the solid and liquid have the same vapor pressure Boiling point-temperature at which the vapor pressure is equal to 1 atm (atmospheric pressure) Boiling point-temperature at which the vapor pressure is equal to 1 atm (atmospheric pressure) Melting and boiling points are higher when the intermolecular forces are stronger Melting and boiling points are higher when the intermolecular forces are stronger

36. Which of the following has the highest boiling point? 1. H 2 O 2. HF 3. HI 4. HBr

37. Which of the following liquids will be the most viscous? 1. C 3 H 8 2. C 6 H 6 3. CH 4 4. C 2 H 6

38. Arrange the following liquids, A, B, C, with vapor pressures at room temperature of 88, 680, and 155, respectively, in order of decreasing boiling points. 1. B>C>A 2. A>B>C 3. A>C>B 4. C>A>B

39. Knowing that solutes with a certain polarity are best dissolved in solutions with similar polarity, which of the following solvents would be optimal for the solvation of CH 3 COOH? 1. CH 4 2. CH 3 OH 3. C 2 H 6 4. C 6 H 6